Domiciled in UK, but how should I deal with foreign income earned (and taxed) in Germany

To date I have always paid taxes via PAYE which my employer has deducted at source. I live in Scotland and I have not had any other sources of income other than my university salary. In addition to my job in the UK (where I am domiciled) I have a 0.2 FTE position at a German University. My monthly pay is roughly 1,520 Euros and, once the tax has been deducted by the German tax authorities I am left with with roughly 1,025 Euros. What do I need to do in order to comply with HMRC requirements? Will I have to pay additional tax on my German-sourced income? Would I be entitled to a tax rebate on my German income? I apologise in advance iff these questions seem very naive - but this is the first time I have had to deal with something g like this.

Hi,
You can see guidance here:
Tax on foreign income
Thank you.